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U0181 Lost Communication With Headlamp Leveling Control Module

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U0181 says the module that controls automatic headlamp levelling has dropped off the bus. That module reads ride-height sensors on the axles and drives the actuator motors in the headlamps to keep the beam at the right angle under load. GM uses the code: the Saab 9-5 (2010-2011) U-code list names it Lost Communication With Headlamp Leveling Control Module, and a GM bulletin for the 2017-2021 GMC Acadia and Cadillac XT5 lists U0181 among the U-codes caused by a chafed dash harness or water in the BCM. Per GM it sets when the module's supervised periodic message is missing at 9-16 V. U0180 is the automatic lighting module, U0182 and U0183 the front and rear lighting modules. No MIL; beam height may stay fixed.

Likely causes

Levelling module without power or ground
Chafed harness or water in connectors or BCM area (GM Acadia/XT5)
Corroded connector at the module near the headlamp
Headlamp levelling module faulty or not coded

Symptoms

  • Headlamp beam height no longer adjusts
  • Headlamp or lighting warning in the cluster
  • Oncoming traffic dazzled or road poorly lit when loaded

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–700
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

headlamp leveling modulecan bus wiring

Related codes

U0180U0182U0183U0140

References: saabwisonline.com, static.nhtsa.gov, saabwisonline.com, hella.com.